According to Popper there is no theory independent observation.
So ''I have seen with my own eye'' or ''I have heard with my own
ears'' is no argument at all. What we hear or see our brain need
to interpret in the context of some premisses.
Take ''our'' scientist Lew as example. He own 5 TT's but neither
of them is belt driven. Does he have some prejudice against belt
driven TT? The most of his TT's are DD kind. So presumably he
has some premises about drive systems in the sense of , say,
quality. Can he hear any difference between his TT's by listening
to them ''naked'' next to each other? Well this may be the case
with his Lenco because its driving system may produce some
''rumble'' which is difficult to supress. That is why he made 100kg.
plinth for the precious (grin). But hearing whatever from his DD
TT's is not probable. This would imply that something is wrong
with the one with, say, sound on its own.
So this thread is at least not clear formulated. One can only
''hear'' an TT in combo with an record , tonearm and cart. The
last mentioned 3 are those which (re)produce sound.